On Tue, Jun 23, 2009 at 10:53 AM, Yong Wang<yong.y.wang@linux.intel.com> wrote:> On Tue, Jun 23, 2009 at 10:40:45AM +0200, stephane eranian wrote:>> Yong,>>>> On Tue, Jun 23, 2009 at 10:27 AM, stephane>> eranian<eranian@googlemail.com> wrote:>> > Hi,>> >>> > On Tue, Jun 23, 2009 at 9:59 AM, Yong Wang<yong.y.wang@linux.intel.com> wrote:>> >> On Tue, Jun 23, 2009 at 09:45:03AM +0200, stephane eranian wrote:>> >>>>> >>> Unfortunately, I don't have a N270 to compare with your results.>> >>> We need to verify whether or not N270 implements the fixed counters.>> >>> Does it report architected perfmon v3 or v1?>> >>>>> >>>> >> All Atom processors report perfmon v3 as specified in SDM. N270 is no>> >> exception.>> >>>> > V3 does not set a minimal number of fixed counters, could be zero. But>> > that seems>> > odd. Let me ask around.>> >>> Second thought on this:>> x86_pmu.num_counters_fixed =>> max((int)edx.split.num_counters_fixed, 3);>>>> rdmsrl(MSR_CORE_PERF_GLOBAL_CTRL, x86_pmu.intel_ctrl);>>>>>> Forcing num_counter_fixed is not enough, you need to make sure they are actually>> activated in GLOBAL_CTRL, i.e., make sure bits 32-34 are set in intel_ctrl.>> Depending on which machine you're on, the power on value for GLOBAL_CTRL>> changes. The correct value for it should be that ONLY generic counters are on>> by default.>>>> Oh, this might be why fixed counter do not work on my Atom box. I will> look into it. BTW, why should ONLY generic counters be on by default?>Glad you asked.I think, it's for backward compatibility with processors such as Core Duo witharchitected perfmon v1 which did not have the GLOBAL_* controls.--To unsubscribe from this list: send the line "unsubscribe linux-kernel" inthe body of a message to majordomo@vger.kernel.orgMore majordomo info at http://vger.kernel.org/majordomo-info.htmlPlease read the FAQ at http://www.tux.org/lkml/